Japan's Kei Nishikori got his first win in a year at the Italian Open on Monday with former Rome semi-finalists Grigor Dimitrov and Marin Cilic also easing into the second round of the clay-court tournament.
Nishikori needed six match points to get past Spain's Albert Ramos-Vinolas 6-4, 7-6 (7/3) in two hours behind closed doors at the Foro Italico for his first win since reaching the 2019 US Open third round.
"It's been a long time since the US Open last year," said the 30-year-old, who reached three Grand Slam quarter-finals in 2019 before undergoing elbow surgery.
"I still don't have confidence but little by little I'm getting better."
Nishikori will next meet either three-time Grand Slam champion Stan Wawrinka, or Italian qualifier Lorenzo Musetti, as he builds his fitness towards the French Open later this month.
The Japanese player skipped the US hard court tour, opting to warm up on clay at Kitzbuehel, Austria last week.
"It sucks missing Grand Slam, big tournaments, but this year is going to be a little bit strange anyways," he said.
"I wanted to come back for the US Open and Cincinnati, but I felt like I wasn't ready for playing five sets, so I chose to play last week in Austria.
"I'm not rushing myself to be 100%. For me, I think this year is going to be one by one, one match at a time.
"I think slowly I'm getting recovered. It will take some time, but I'm happy to be here in Rome.
"Today was much better than last match last week. I would say twice better."
Top seeds Novak Djokovic, a four-time Rome winner, and defending champion Rafael Nadal, winner nine times, have first round byes in a tournament rescheduled from May due to the coronavirus pandemic. They will begin their campaigns on Wednesday.
Elsewhere 15th seed Dimitrov, a 2014 Rome semi-finalist, saw off Italian wild card Gianluca Mager 7-5, 6-1.
Bulgarian Dimitrov pulled ahead from 5-5 in the first set to win seven straight games and next meets either Yoshihito Nishioka or Kitzbuehel champion Miomir Kecmanovic.
Cilic, who lost to Alexander Zverev in the Rome semi-finals two years ago, battled past Kazakhstan's Alexander Bublik 6-7 (4/7), 6-2, 6-4 for a second round meeting with sixth seed David Goffin.
France's Benoit Paire, who was removed from the US Open after testing positive for Covid-19, lost his opener 6-2, 6-1 to Italian teen Jannik Sinner.
The 19-year-old Sinner, ranked 81, needed just over an hour to advance following a nervy performance by the 24th-ranked French player.
Next Gen ATP Finals champion Sinner will play third seed Stefanos Tsitsipas of Greece in the next round.
US Open quarter-finalist Borna Coric eased past 14th seed Cristian Garin 6-4, 6-4, while Frenchman Ugo Humbert defeated two-time Grand Slam finalist Kevin Anderson 6-3, 7-6 (7/5) in his Rome debut.
He will try to upset seventh seeded Italian Fabio Fognini in the second round.
In the women's tournament, US Open quarter-finalist Elise Mertens showed no problems switching from hard court to clay with the 11th seed disposing of Taiwan's Hsieh Su-Wei 6-3, 6-1.
"My serve was better in the second set, which made all the difference," said the Belgian.
Italian wildcard Jasmine Paolini eased past Latvia's Anastasija Sevastova 6-2, 6-3 to earn a second round clash with top seed Simona Halep of Romania.
Second seed Karolina Pliskova opens her title defence against fellow Czech Barbora Strycova who strolled past Russian Veronika Kudermetova 6-3, 6-3.
Collated results from the first day of the ATP and WTA clay-court tournament in Rome on Monday (x denotes seed):
Filip Krajinovic (SRB) bt Felix Auger-Aliassime (CAN x16) 6-4, 7-5
Casper Ruud (NOR) bt Karen Khachanov (RUS x11) 6-3, 3-6, 6-1
Kei Nishikori (JPN) bt Albert Ramos-Vinolas(ESP) 6-4, 7-6 (7/3)
Stefano Travaglia (ITA) bt Taylor Fritz (USA) 6-4, 7-6 (7/4)
Borna Coric (CRO) bt Cristian Garin (CHI x14) 6-4, 6-4
Lorenzo Sonego (ITA) bt Nikoloz Basilashvili (GEO) 6-3, 6-1
Marin Cilic (CRO) bt Alexander Bublik (KAZ) 6-7 (4/7), 6-2, 6-4
Ugo Humbert (FRA) bt Kevin Anderson (RSA) 6-3, 7-6 (7/5)
Grigor Dimitrov (BUL x15) bt Gianluca Mager (ITA) 7-5, 6-1
Jannik Sinner (ITA) bt Benoit Paire (FRA) 6-2, 6-1
Hubert Hurkacz (POL) bt Dan Evans (GBR) 6-3, 3-6, 7-5
Jasmine Paolini (ITA) bt Anastasija Sevastova (LAT) 6-2, 6-3
Dayana Yastremska (UKR) bt Camila Giorgi (ITA) 7-5, 6-7 (5/7), 6-4
Amanda Anisimova (USA) bt Donna Vekic (CRO x16) 7-6 (7/4), 7-6 (8/6)
Elena Rybakina (KAZ x10) bt Ekaterina Alexandrova (RUS) 6-0, 6-4
Marie Bouzkova (CZE) bt Ajla Tomljanovic (AUS) 6-3, 6-4
Danka Kovinic (MNE) bt Julia Goerges (GER) 6-1, 6-0
Magda Linette (POL) bt Jelena Ostapenko (LAT) 6-4, 6-3
Elise Mertens (BEL x11) bt Hsieh Su-Wei (TPE) 6-3, 6-1
Aliona Bolsova (ESP) bt Alison Riske (USA x13) 5-7, 7-6 (7/4), 6-3
Anna Blinkova (RUS) bt Jil Teichmann (SUI) 6-3, 6-3
Barbora Strycova (CZE) bt Veronika Kudermetova (RUS) 6-3, 6-3